Seal means for blood separator and the like



July 7, 197() R 1 EISEL ET AL SQ SEAL MEANS FOR BLOOD SEPARATOR AND THE LIKE Filed May '7, 1968 2 Sheets-Sheet l IOO /f// @o l MMM/m4 m8x /OZ 4,0 /gl v50 E G4 e Tl aff/45445470131,:152m 4e e@ l0 14 04989/14123/ es 16 e 0 z "LG @all l w La A w--fx july 7, fg@ R- J ElsEL ET AL 3,59,

SEAL MEANS FOR BLOOD SEPARATOR AND THE LIKE Filed May '7, 1968 2 Sheets-Sheet 2 United States Patent O 3,519,201 SEAL MEANS FOR BLOOD SEPARATOR AND THE LIKE Robert J. Eisel, Kensington, and William B. Greenough III, Baltimore, Md., and Robert M. Kellogg, Endwell, N.Y., assignors to the United States of America as represented by the Secretary, Department of Health, Education, and Welfare Filed May 7, 1968, Ser. No. 727,192 Int. Cl. B04b 11/00; A61m 5/00 U.S. Cl. 233-21 10 Claims ABSTRACT F THE DISCLOSURE Sealing means for use with a face seal having one fixed element and one rotating element particularly for use with a continuous blood flow separator. Saline under pressure is forced into groove means between the channel means at the interface of the seal means to preclude seepage of the materials in the channel means across the interface. According to a preferred arrangement the most sensitive material, such as packed red blood cells, is removed through the most direct pathway to preclude damage thereto. Preferably, the rotating element is formed of ceramic and the fixed element is formed of stainless steel.

This invention relates to a sealing means for use with a face seal having one fixed element and one rotating element. More specifically, this invention is directed to a modi-tied and improved sealing means for use with a continuous flow blood separator of the type described in detail in copending application Ser. No. 570,792 filed Aug. 8, 1966, in the names of George T. Judson and Emil J. Freireich, and assigned to the same assignee as the instant application. The disclosure of the aforementioned copending application is incorporated herein by reference in its entirety.

The provision of a sealing means between fixed and rotating elements provides obvious difficulties. Such a sealing means has general applicability, for example, in centrifuge devices or separating means wherein a fluid is separated into a plurality of components by centrifugal force. With such devices the fluid must be fed into the bowl of the centrifuge and the separated components of the fluid must be removed therefrom after centrifugation. Since portions of the centrifuge are rotating at high speeds, and since the source of the fluid and the depository for the components are usually stationary, a sealing means must be interposed which is effective to prevent leakage between a stationary or xed element into which the fluid is fed and from which the components are withdrawn, and a rotating element which receives the iiuid from the xed element and feeds the same to the bowl of the separator and which receives the fractional components from the separator and feeds the same to the fixed element for withdrawal from the device. The difficulties of such an operation are believed obvious.

Such difficulties are'compounded when the fluid being separated is blood or any other material particularly sensitive to damage. Further, when the fluid is blood withdrawn directly from a donor, with certain of the fractional components being returned directly to the donor in a continuous separation system, any damage to the components has even greater significance since there is relatively little opportunity to monitor the same before they are returned to the donor. The aforementioned copending application discloses such a continuous flow blood separator and provides a face seal adapted to prevent leakage between the fixed and rotating elements of the centrifuge thereof. This face seal, while "ice generally satisfactory, has been subject to certain problerns. Particularly, it has been found that in some instances the blood or fractional components thereof have a tendency to seep across the lands separating the channels defined at the interface between the fixed and rotating elements. In addition to such seepage causing a mixture of the various materials which in itself is undesirable, the high shear to which such materials are subjected during seepage across the interface has been found to damage the materials. It is this problem with which the instant invention is primarily concerned.

Other difficulties have also been encountered with the face seal disclosed in the aforementioned copending application. One of the fractional components being separated from the blood is packed red blood cells, a material which is particularly sensitive. In the face seal of the copending application, the blood itself is fed through a central axial passageway which extends through both the fixed and rotating elements, and the fractional components are withdrawn through aligned concentric channels in the fixed and rotating elements. Removal of the packed red blood cells through one of the annular channels necessitates the passage of this material through a somewhat tortuous route. It is preferred that this particularly sensitive component of the blood be handled in the most delicate manner and the instant inventive concepts modify the face seal of the copending application to effect this result.

One further difiiculty found with the sealing means of the prior application results from the preferred material utilized in the manufacture of the rotating element. A synthetic resin, specifically polytetrafluoroethylene (Teflon), was initially utilized for the formation of the rotating element, but it has now been found that this material is subject to warping in use. Due to the necessity for extremely accurate mating of the fixed and rotating elements, even slight dimensional changes of the rotating element can reduce the effectiveness of the seal. The instant invention replaces the Teflon rotating element with an element formed of a material which is dimensionally stable under the conditions of use.

Although the instant inventive concepts are applicable to any sealing means wherein fixed and rotating elements are found, since the most important application of the sealing means is in a continuous flow blood separator of the type disclosed in the aforementioned copending application, the preferred embodiments hereof will be discussed in relation thereto.

`Considering the foregoing, it is a primary object of the instant invention to provide a sealing means of the type described which is free from the foregoing and other such disadvantages. A basic and important objective of this invention is the provision of a sealing means which precludes lateral seepage of blood or fractional components thereof across the interface defined between the fixed and rotating elements. In this regard, the instant inventive concepts provide means intermediate each juxtaposed pair of channels in the face seal which acts as a barrier to such seepage.

Yet another important object of the instant invention is the provision of an arrangement for a face seal wherein the most sensitive component, that is, the packed red blood cells, are passed through the most direct path to preclude any damage thereto.

Further, another important object of this invention is the provision of a face seal wherein the rotating element is formed of a material which is not subject to dimensional change or warpage during use.

Other and further objects of the instant inventive concepts will either be specifically mentioned in the following detailed description or will be obvious therefrom.

3 Such detailed description makes reference to the accompanying drawing wherein:

FIG. 1 is a vertical cross-sectional view through a centrifuge means incorporating a face seal according to the instant inventive concepts;

FIG. 2 is a bottom plan view of the fixed or stationary element of the face seal;

FIG. 3 is a transverse cross-sectional view taken substantially on lines 3--3 of FIG. 2;

FIG. 4 is a top plan view of the rotating element of the face seal; and

FIG. 5 is a transverse cross-sectional view taken substantially on lines 5-5 of FIG. 4, showing cooperating portions of the centrifuge means in dotted lines.

Like reference characters refer to like parts throughout the several views of the drawing.

Reference may be made to the aforementioned copending application which, as has been mentioned hereinabove, is incorporated herein by reference in its entirety, to provide further background on the preferred system with which the improvements of the instant application may be utilized. In such system, whole blood is withdrawn directly from a donor, separated in a centrifuge means into red blood cells, white blood cells or buffy coat and plasma, with one or more of the fractional components being returned directly to the donor from the centrifuge means. Of course, various safety devices are included in the system and the use of these devices would be equally applicable to the means of the instant invention. Additionally, platelets can be withdrawn either with the white blood cells or 'with the plasma and subsequently separated in a second centrifuge, if desired. Further, the various operating means including pumps and the like shown. in the aforementioned copending application are all applicable to use with the modified means of the instant invention.

The basic centrifuge means is designated generally by the reference numeral in FIG. l and includes a bowl or shell y12 disposed within a casing (not shown) which is utilized to rotate the bowl and its associated elements about a central axis. The shell 12 has an upstanding cylindrical sidewall means 14 Which terminates in an outwardly and upwardly directed flange 16. The bottom wall 18 of the shell 12 is provided with an annular depending flange 20y and a central spindle 22 utilized for centering the shell 12 with respect to the outer casing.

The interior of the sidewalls 14 of the shell 12 serve to provide the outer boundary for the separation channel 24. Starting iat the top of the shell 12, a wall portion 26 extends linearly downwardly for a predetermined distance, then merges smoothly into an inwardly and downwardly inclined wall portion 28 which in turn merges into another linearly extending wall portion 30.

Another portion of the centrifuge assembly or separating means 10 is the center or filler piece designated generally by the reference number 32. This filler piece is suitably suspended within the shell 12 in a manner to be more fully described hereinafter. A central bore 34 extends completely from the lower surface 36 of the ller piece 32 to the upper surface thereof. A depression 38 is provided in the upper surface 40 of the ller piece 32 and an O-ring 42 seals this depression 38 against a protrusion 44 on the cover member 46 thereby providing an enlarged cavity 48. This bore 34 provides the input channel for the blood and the cavity 48 permits communication between the bore 34 which is axial and radially offset passageway means 50 for carrying the blood from the seal means in a manner to be described in more `detail hereinafter. This arrangement dilfers from the construction of the separating means in the aforementioned copending application and permits the use of the axial passageway means into the seal means for packed red blood cells which are more sensitive to damage than the whole blood itself.

The ller piece 32 is cylindrically shaped for the most part and of a somewhat smaller diameter than that of the shell wall portion 30. As such, the outer or sidewall 52 of the filler piece 32 is spaced slightly away from the wall portion 30 to thereby provide the other boundary of the separation channel 24. This channel extends with uniform thickness substantially for the height of the shell wall portion 30. Substantially opposite to the inclined portion 28 of the centrifuge shell, the sidewall 52 of the ller piece is radially curved as shown at 54. This curve merges into an inwardly extending shoulder portion 56 which again turns into an upwardly extending portion at 58 to blend into the top surface 40.

The filler piece 32 is secured to the cover member 46 by bolts or the like 60 which also function to secure a holding member 62 in the related assembly.

The top cover 46 is preferably fabricated of a clear plastic material 'which permits visual observation of the separation occurring within the centrifuge. This top cover member includes a flange portion 64 which abuts against the top of the flange portion 16 of the centrifuge shell 12 with bolts 66 securing these elements in related assembly. Gasket means (not shown) are included to preclude against leakage between these parts. Additionally, the flange portion 64 of the cover member 46 includes an angularly offset portion 68 designed to rest upon, and be frictionally driven by, a driving means (not shown). This manner of rotating the separating means differs slightly from the construction shown in the aforementioned application and has been found to provide better overall operation.

A short vertical wall portion 70 extends downwardly from the ange portion 64 of the top cover 46 to mate contiguously with the Wall portion 26 of the centrifuge shell 12, thereby properly positioning the cover on the shell. At the end of the vertical wall portion 70, there is a horizontally or radially inwardly stepped portion 72 which merges with the top of another short vertical 'wall portion 74. At the bottom of the wall portion 74, there is another radially inwardly stepped portion 76 which merges with the top of a further vertical wall portion 78. The bottom of this vertical wall portion 78 merges with the bottom surface 80` of the cover member 46 which rests on the top surface 40 of the ller piece 32.

The `attachment of the filler piece 32 to the cover member 46 is arranged such that the bottom surface 36 of the filler piece 32 is spaced slightly from the bottom inner surface 82 of the shell 12 to provide a channel 84 through which the whole blood flowing through the bore 34 can spread outwardly to the separation channel 24 and then climb upwardly therealong as the centrifuge is operated.

The seal means of the instant invention is designated generally by the reference numeral and includes a lower or rotating element 102 and an upper or stationary element 104. The lower or rotating element 102 fits within a rst stepped recess or portion 106 on the top of the cover member 46. A second stepped recess or portion 108 is also provided in the top of the cover member 46 with the stepped portion 108 being somewhat smaller than the stepped portion 106. The stepped portion 108 contains a plurality of spaced grooves concentrically arranged around the central axis thereof with O-rings having a rectangular cross-sectional configuration being mounted within each of these grooves. All of the O-rings have been designated generally by the reference numeral 110, but it will be appreciated that the size or diameter of such O-rings continually increases. Since the bottom of the rotating element 102 abuts against the top of the various O-rings 110, the overall effect of such arrangement is to set olf a series of channels or annular spaces between the stepped portion 108 and the bottom of the rotating element 102. The smallest or innermost O-ring 110 defines therewithin a circular opening or channel means designated 112, with such channel means being axially aligned with the central or rotational axis of the centrifuge means 10. Between this innermost O-ring and the next adjacent O-ring, a first annular channel means 114 is formed. Between the second O-ring and the next adjacent O-ring, a second annular channel 116 is formed. Finally, between said next adjacent O-ring and the outermost O-ring, a third or outer annular channel means 118 is formed. Each of these channel means serves to receive either the whole blood or the one of the fractional components as will be explained in more detail hereinafter.

To more fully understand the nature of the separation or fractionation which occurs within the centrifuge means 10, it can be seen that the separation channel 24, preferably having an optimum radial dimension of approximately l mm., extends upwardly with uniform thickness until it reaches the inclined wall portion 28 of the centrifuge shell 12. At this point, the separation channel 24 merges into an enlarged separation space 120. When whole blood enters the centrifuge means it travels downwardly through the central bore 34, then outwardly in the separation channel 84 and upwardly through the separation channel 24 to enter the space 120. Such climbing action is created by a combination of the centrifugal force generated by rotation of the centrifugal shell 12, the filler piece 32 and the top cover 46 and the action of the various pumps described in more detail in the aformentioned copending application. Due to this centrifugal force, the whole blood starts to separate as it begins to climb through the separation channel 24 and due to the difference in specific gravities of the various fractions thereof. The packed red cells are the most dense of the fractions, and these are thus packed outermost within the space 120. The white cells are the next most dense and these are thus positioned adjacent the red cells and the plasma is the least dense and hence is disposed furtherest inwardly within the centrifuge. For purposes of illustration, blood is shown in the bore 34, in the separation channel 84 and in the lower portion of the separation channel 24. The packed red cells are designated R, the white cells are designated W, and the plasma is designated P. The various fractions are fully separated in the separation space 120 and the quantity of white cells is extremely small whereby, initially, there is merely an interface between the plasma P and the packed red cells R. Proper regulation of the various pumps associated with the separation system, as explained in more detail in the aforementioned copending application, adjusts the plasmared cell interface line to space the same closer to the shell wall 26 or further away therefrom. However, after the blood has been separating for awhile, the white cells W start to build up within the centrifuge to form a buffy coat of the shape generally illustrated in FIG. 1. It will be seen that the white cell layer effectively oats between the red cells and plasma.

A first radial channel 124 communicates at one end with the separation space 120 at the wall portion 58 to receive the layer of plasma, and this radial channel 124 turns upwardly at 126 to communicate at its opposite end with the channel means 118 for removal of plasma P through the seal means 100. A second radial channel 128 communicates at one end with the separation space 120 at the wall portion 78 and turns upwardly as at 130 to communicate at its opposite end with the channel means 116 for removal of white blood cells W through the seal means 100. A third radial channel 132 communicates at one end with the separation space 120 at the wall portion 74 and turns upwardly as at 134 to lform a portion which is co-axial with the center of rotation of the centrifuge means 10 and which communicates at its opposite end with the channel means 112 for removal of the packed red blood cells R through the seal means 100. Thus, each of the individual fractions of the blood is transferred to its own particular channel means between the top cover 46 and the seal means 100.

Although only a single channel has been shown communicating the separation space with the individual channel means defined between the top cover 46 and the seal means 100, it will be understood that such an arrangement is illustrative and a plurality of ports or channels can be provided to carry each of the fractional components of the blood to their respective channel means. Additionally, as will be readily understood that those skilled in the art, these fractional components are withdrawn from the separating means 10 with the aid of pumps as explained in more det-ail in the aforementioned copending patent application.

To understand the nature and construction of the seal means 100, attention is directed particularly to FIGS. 2-5 which show in further detail the rotating element 102 and the fixed element 104. The rotating element 102 is preferably formed of a ceramic material which has been found to ibe dimensionally stable under the conditions of use. As mentioned previously, it was found that Teiion had a tendency to warp from the heat of the blood and the operation of the device causing a reduction in the effectiveness of the seal. Manufacture of the rotating element 102 from ceramic material precludes this disadvantage. The rotating element 102 has a circular base portion 140 with a at bottom surface 142. The size of this base portion corresponds substantially to the size of the stepped portion 106 in the cover member 46 and, as mentioned previously, when the rotating element 102 is positioned within the top cover 46, the bottom surface 142 abuts against the top of the O-rings 110. To prevent relative rotation between the rotating element 102 and the cover member 46, a small notch 144 can be provided in the periphery of the base portion 140, if desired. This notch 144 may mate With a guide pin 146 positioned at one edge of the stepped recess 106 in the top cover 46. Further means of securing the rotating element 102 to the top cover 46 comprises the pressure plate 62 which includes an inwardly directed ange 148 which seats over the base portion 140 of the rotating element 102 as shown in FIG. 1. The bolts 60 function to secure this element to the filler piece 32 through the top cover 46 thereby securing the entire assembly together. Alternatively, separate bolts may be utilized to secure the cover member 46 to the filler piece 32 and to secure the pressure plate 62 to the cover member 46. Further, the pressure plate 62 may merely function to assist in securing the rotating element 102 in position, with its primary function being as a handle to facilitate removal of the centrifuge means 10 from the casing (not shown) in which it is mounted in the assembly. To this end, an outstanding peripheral flange 150 may be provided on the pressure plate or handle 62.

The rotating element 102 also includes an upstanding cylindrical body portion 152 integral with the base portion 140, but having a cross-sectional diameter somewhat smaller than that of the base portion 140. The top surface 154 of the rotating element 102 is planar according to the instant inventive concepts, although, if desired, mating portions of the channel means and groove means defined in the fixed element 104 and to be described in more detail hereinafter, may be provided in the top surface 154. However, it has been found that a better seal is provided if this element has a planar top surface.

At the center of the rotating element 102, a central bore 156 is provided which functions as a passageway means for withdrawing packed red blood cells from the channel means 112 through the rotating element 102. The upper portion of this passageway means 156 and the lower portion of an aligned passageway means in the fixed element 104 to be described in more detail hereinafter together define a channel means for the red blood cells at the interface between these elements.

In addition to the central bore or passageway means 156 a plurality of additional bores or passageway means 158 are arranged concentrically about the central bore 156 in communication with the channel means 114 and in communication with the channel means for the whole blood to lbe provided at the interface between the rotating and fixed elements as described in more detail hereinafter. Additional concentrically arranged bores or passageway means 160 are provided in communication with the channel means 116 for carrying white blood cells through the rotating element 102 and still further concentrically arranged bores or passageway means 162 are provided to communicate with the channel means 118 for carrying plasma through the rotating element 102. The bores 158, 160 and 162, as will be seen from the drawing, are arranged on concentric circles of increasing diameter. These circles correspond to the mean diameters of the channel means provided at the interface between the fixed and rotating elements as will be explained in further detail hereinafter.

As mentioned previously, the fixed element 102 is formed of ceramic and thus, is not subject to dimensional change or instability during use.

As will be seen, there is a series of annular lands formed by the top surface 154 of the rotating element 102. These lands act as boundaries between the various passageway means, and as will be explained in further detail hereinafter, cooperate with certain groove means in the fixed element 104 to preclude cross-over or seepage between the various channel means carrying the whole blood and fractional components thereof.

By referring now more particularly to FIGS. 2 and 3, the exact nature of the upper or fixed seal means 104 will be better understood. This element is preferably formed of stainless steel and has a fiat lower surface 164 Which is preferably lapped to a fiatness of 3 light waves or less and which rests on the upper surface 154 of the rotating element 102, this upper surface 154 also preferably being lapped to a iiatness of 3 light waves or less. A central bore 166 is defined in the fixed element 104 and is aligned with the central bore 156 of the rotating element 102 to receive the packed red blood cells therefrom and pass the same to tubing 167 for removal from the separating means 10. This use of a continuous central bore through the seal means 100 to carry the packed red blood cells functions to provide a more direct pathway for the red blood cells which, as mentioned, previously, are particularly sensitive. Concentrically arranged annular channel means 168, 170 and 172 are designed to mate with the openings at the tops of the passageway means 158, 160 and 162 in the rotating element 102. Bores or passageway means 174, 176 and 178 communicate with the channel means 168, 170 and 172 respectively at one end and with flexible tubing 180, 182 and 184 at their opposite ends. In this manner, whole blood is passed, from a source of the same, in a continuous blood separator, from the donor, through the tubing 180 to bore 174, the channel means 168, the passageway means 158, the channel means 114, the bore 50 and the cavity 48 to the separating means. White blood cells pass from the separating means through the channel means 116, the passageway means 160, the channel means 170, the passageway means 176 and the tubing 182 to any desired location. The plasma, when received from the separating means 10, passes through the channel means 118, the passageway mean 162, the channel means 172, the passageway means 178 and the tubing 184 to any desired location, generally back to the donor in a continuous blood separator.

Finally, an annular channel means 190 is provided in the fixed element 104 to define a saline-receiving channel to cool the seal means 100 and to provide an air barrier to protect the blood and other fractional components in the remainder of the seal means 100 against the entrance of air. Tubing 192 communicates through a bore 194 with this outer channel means for introduction, generally by gravity, of saline to the channel means 190 and tubing 196 communicates with the channel means 190 through a bore 198 for slow removal of saline therefrom. A clamp or the like (not shown) may be utilized on the tubing 196 to regulate removal of saline from the channel means 190.

A mojor feature of the instant inventive concepts is the provision of groove means 200 in the lands separating the various channel means in the fixed element 104. These groove means 200 communicate through a passageway means 202 with a tube 204. Saline under pressure is fed through the tube 204 to the groove means 200. The pressure of the saline in these groove means is at least as great as the pressure of the blood or the fractional components thereof in the various channel means. With a continuous flow blood separator of the type shown in the aforementioned copending application, the blood could be under arterial pressure whereby the pressure of the saline in the groove means 200 is at least this great. Preferably, saline is forced into the groove means 200 at a pressure in excess of arterial pressure. Arterial pressure is generally considered to be about 200 mrn. of mercury and the pres sure behind the saline in the groove means 200 is preferably from about 10-12 p.s.i. at a iiow rate of about 20 ml./hr. Thus, a portion of the saline is caused to iiow laterally from earh of the groove means arross the interface toward juxtaposed channel means to assist in precluding seepage of the blood and components across the interface which, as mentioned previously, may damage the various materials in the channel means and may cause mixing of the same. Leakage of the saline from the outer groove means 200 around the periphery of the seal means will not cause any difficulty and will merely fiow downwardly into the separating means 10.

Reference may be made to the aforementioned copending application wherein a pivotally carried arm means is shown which cooperates with the seal means to press downwardly on the fixed element 104 during use. This arm means (not shown herein) may be readily raised to remove the centrifuge assembly when desired.

It is believed that the operation of the separating means will be readily understood from the foregoing detailed descirption. It can be seen that there is herein provided an improved construction of such separating means, and particularly the seal means thereof, which satisfies all of the objectives of the instant invention and others, including many advantages of great practical utility and commercial importance. Since many embodiments may be made of the instant inventive concepts, and since many modifications may be made of the embodiments herein before shown and described, it is to be understood that all matter is to be interpreted merely as illustrative and not in a limiting sense.

Accordingly, what is claimed is:

1. In a blood separator of the type wherein means are provided for separating blood from a source of the` same into a plurality of fractional components, said blood separator having seal means associated with the separating means, said seal means including a fixed element and a rotating element having portions which abuttingly engage each other to define an interface therebetween, portions of said seal means defining spaced channel means at said interface for receiving in different channel means either blood to be separated from said source or fractional components of the separated blood from said separating means, and separate passageway means communicating with said seal means for bringing said blood to one of said channel means from said source through said fixed element, for feeding said blood from said one channel means to said separating means through said rotating element, for bringing said fractional components of said blood from said separating means to others of said channel means through said rotating element, and for withdrawing said fractional components from said other channel means through said fixed element, the improvement which comprises:

(a) portions of said seal means defining groove means at said interface between said pair of juxtaposed channel means, and

(b) means for feeding saline solution into each of said groove means at a pressure at least as great as the pressure of said blood and fractional components thereof in said juxtaposed channel means.

2. The improvement of claim 1 wherein said blood separator includes means for continuously withdrawing blood from a donor and means for continuously returning at least one of said fractional components thereof to the donor after separation, said saline feeding means forcing saline into each of said groove means at a pressure at least equal to arterial pressure.

3. The improvement of claim 2 wherein said saline feeding means forces saline into each of said groove means at a pressure in excess of arterial pressure.

4. The improvement of claim 1 wherein said saline feeding means forces saline into each of said groove means at a pressure suicient to cause a portion of said saline to flow laterally from each of said groove means across said interface toward juxtaposed channel means.

5. The improvement of claim 1 wherein said channel means includes a central channel means coincident with the axis of rotation of said seal means and at least two circular channel means concentric with said central channel means, said circular channel means being radially spaced from said central channel means and from each other, said groove means being provided at least between said central channel means and the rst concentric circular channel means and between each additional pair of juxtaposed circular channel means.

6. The improvement of claim S wherein one of said fractional components includes packed red blood cells, said passageway means including an axial passageway means in said rotating element communicating the portion of said separating means containing said packed red blood cells with said central channel means and an axial passageway means in said fixed element communicating with said central channel means for withdrawing said red blood cells from said seal means.

7. The improvement of claim 1 further including portions of said seal means defining an outer channel means at said interface for receiving saline solution to cool said seal means and to provide an air barrier to protect said blood and said fractional components in the remainder of said channel means, means for feeding saline solution to said outer channel means, and means for slowly removing said saline solution from said outer channel means.

8. The improvement of claim 1 wherein said xed and rotating elements each have a planar face portion, said planar face portions abutting each other and together deining said interface, and all of said channel means and all of said groove means being delined in said planar face portion of said xed element.

9. The improvement of claim 8 wherein said rotating element is formed of ceramic.

10'. The improvement of claim 9 wherein said xed element is formed of stainless steel.

References Cited UNITED STATES PATENTS 2,822,126 2/1958 `Cohn 233-1 2,876,769 3/1959 Cordova 23-2585 3,145,713 8/1964 Latham 128-214 3,195,809 7/1965 Pickels et al. 233-21 3,231,184 1/1966 Podbielniak 233-21 X 3,292,937 12/1966 Nunley 277-59 3,443,747 5/1969 Jacobson et al. 233-22 DALTON L. TRULUCK, Primary Examiner U.S. Cl. X.R. 

